Researchers at the Wyss Institute for Biologically Inspired Engineering at Harvard University have unveiled a new method to form tiny 3D metal nanoparticles in prescribed shapes and dimensions using DNA, Nature's building block, as a construction mold.
The ability to mold inorganic nanoparticles out of materials such as gold and silver in precisely designed 3D shapes is a significant breakthrough that has the potential to advance laser technology, microscopy, solar cells, electronics, environmental testing, disease detection and more.
For the very first time, a general strategy to manufacture inorganic nanoparticles with user-specified 3D shapes has been achieved to produce particles as small as 25 nanometers or less, with remarkable precision (less than 5 nanometers). A sheet of paper is approximately 100,000 nanometers thick.
The 3D inorganic nanoparticles are first conceived and meticulously planned using computer design software. Using the software, the researchers design three–dimensional "frameworks" of the desired size and shape built from linear DNA sequences, which attract and bind to one another in a predictable manner.
Just as any expanding material can be shaped inside a mold to take on a defined 3D form, the Wyss team set out to grow inorganic particles within the confined hollow spaces of stiff DNA nanostructures.
The concept can be likened to the Japanese method of growing watermelons in glass cubes. By nurturing watermelon seeds to maturity inside cube–shaped glass boxes, Japanese farmers create cube-shaped mature melons that allow for densely–packed shipping and storage of the fruit.
The Wyss researchers similarly planted a miniscule gold "seed" inside the hollow cavity of their carefully designed cube–shaped DNA mold and then stimulated it to grow. Using an activating chemical solution, the gold seed grew and expanded to fill all existing space within the DNA framework, resulting in a cuboid nanoparticle with the same dimensions as its mold, with the length, width and height of the particle able to be controlled independently.
Next, researchers fabricated varied 3D polygonal shapes, spheres, and more ambitious structures, such as a 3D Y–shaped nanoparticle and another structure comprising a cuboid shape sandwiched between two spheres, proving that structurally–diverse nanoparticles could be shaped using complex DNA mold designs.
Given their unthinkably small size, it may come as a surprise that stiff DNA molds are proportionally quite robust and strong, able to withstand the pressures of expanding inorganic materials. Although the team selected gold seedlings to cast their nanoparticles, there is a wide range of inorganic nanoparticles that can be forcibly shaped through this process of DNA nanocasting.
A very useful property is that once cast, these nanoparticles can retain the framework of the DNA mold as an outer coating, enabling additional surface modification with impressive nanoscale precision. These coatings can also help scientists develop highly-sensitive, multiplex methods of detecting early–stage cancers and genetic diseases by combining the chemical specificity of the DNA with the signal readout of the metal. For particles that would better serve their purpose by being as electrically conducive as possible, such as in very small nanocomputers and electronic circuitry, the DNA framework coating is quickly and easily broken down and removed to produce pure metal wires and connectors.
"The properties of DNA that allow it to self assemble and encode the building blocks of life have been harnessed, re–purposed and re–imagined for the nano–manufacturing of inorganic materials," said Don Ingber, Wyss Institute founding director. "This capability should open up entirely new strategies for fields ranging from computer miniaturization to energy and pathogen detection."
This story is reprinted from material from Wyss Institute, with editorial changes made by Materials Today. The views expressed in this article do not necessarily represent those of Elsevier. Link to original source.